1. Field of the Invention
An apparatus consistent with the present invention relates to a refrigerant cycle system and, more particularly, to a refrigerant cycle system in which the arrangement of a connecting pipe for connection between a compressor and an accumulator is improved effectively to recover oil collected in the accumulator to the compressor.
2. Description of the Related Art
Refrigerant cycle systems cool or heat air in confined spaces by utilizing phase change of a refrigerant circulating a closed refrigerant circuit including a compressor, a condenser, an expansion unit, and an evaporator, which are appropriately connected to one another by connecting pipes.
The compressor compresses a low temperature and low pressure refrigerant gas to a high temperature and high pressure gas state. The condenser condenses the high temperature and high pressure refrigerant gas discharged from the compressor to a high temperature and high pressure liquid state. The expansion unit expands the high temperature and high pressure refrigerant liquid emerging from the condenser, thereby changing the refrigerant liquid to a low temperature and low pressure liquid state (of course, a small part of the refrigerant liquid may be changed to a gas state). The low temperature and low pressure refrigerant liquid absorbs heat from air in a confined space while passing through the evaporator, so that it is changed to a high temperature and low pressure gas state. The resultant refrigerant is then introduced into the compressor in order to repeat the above processes.
As the refrigerant repeatedly circulates the closed refrigerant circuit of the refrigerant cycle system, the evaporator cools the air in the confined space, thereby lowering the temperature of the confined space. Meanwhile, the condenser emits heat therearound, so that the temperature of ambient air around the condenser increases. Thus, the refrigerant cycle system is used as a refrigerator or a cooling/heating apparatus, by use of heat absorption caused by evaporation and heat emission caused by condensation.
Meanwhile, the refrigerant is typically incompletely changed to a gas state while passing though the evaporator. To this end, an accumulator is arranged between the evaporator and the compressor in order to separate a liquid portion from the refrigerant emerging from the evaporator, so that only the refrigerant gas is introduced into the compressor.
The accumulator may be attached to the compressor so that it is integral with the compressor. Alternatively, it may be separate from the compressor. In the latter case, the accumulator may be connected to the compressor by a connecting pipe. The refrigerant cycle system may be configured to include a plurality of compressors so that it has a variable capacity.
In a conventional refrigerant cycle system having the above mentioned arrangement in which the accumulator is separate from the compressor, the refrigerant gas emerging from the accumulator is fed to the compressor via the connecting pipe. This connecting pipe has an inlet portion received in the accumulator, and an outlet portion received in a lower end portion of the compressor. The portion of the connecting pipe between the inlet and outlet portions has an inverted U shape while being arranged between the accumulator and the compressor.
Meanwhile, oil adapted to lubricate rotating parts of the compressor may partially be included in the refrigerant emerging from the compressor. After circulating the closed refrigerant circuit of the refrigerant cycle system, the oil included in the refrigerant is collected in the accumulator. In order to feed the collected oil to the compressor, an oil recovery hole is provided at the inlet portion of the connecting pipe received in the accumulator.
In the conventional refrigerant cycle system, however, there is a possibility that oil may not be effectively recovered into the compressor because the oil recovery hole is arranged at a level lower than a highest level portion of the connecting pipe. The oil collected in the accumulator is introduced into the inlet portion of the connecting pipe through the oil recovery hole, and then fed to the compressor via the connecting pipe, along with the refrigerant gas introduced into the inlet portion of the connecting pipe. However, the oil is ineffectively recovered into the compressor because the flow rate of the refrigerant gas is relatively low due to the fact that the connecting pipe has a large diameter, as compared to the high viscosity of the oil, and because of the structure in which the oil recovery hole is arranged at a level lower than the highest level portion of the connecting pipe located outside of the accumulator. As a result, there may be a phenomenon that the amount of the lubricating oil in the compressor is insufficient after prolonged use.
In particular, such an oil shortage phenomenon may be severe in a refrigerant cycle system including a common accumulator and a plurality of compressors to allow variable capacity operation. In such a refrigerant cycle system, there may also be a problem in that recovery of oil may be achieved in only one of the compressors. That is, the collected oil may be ineffectively recovered to the other compressor.